diff --git a/src/ssl/support.cc b/src/ssl/support.cc
index 3ad135d..73912ce 100644
--- a/src/ssl/support.cc
+++ b/src/ssl/support.cc
@@ -557,7 +557,11 @@ Ssl::VerifyCallbackParameters::At(Security::Connection &sconn)
 }
 
 // "dup" function for SSL_get_ex_new_index("cert_err_check")
-#if SQUID_USE_CONST_CRYPTO_EX_DATA_DUP
+#if OPENSSL_VERSION_MAJOR >= 3
+static int
+ssl_dupAclChecklist(CRYPTO_EX_DATA *, const CRYPTO_EX_DATA *, void **,
+                    int, long, void *)
+#elif SQUID_USE_CONST_CRYPTO_EX_DATA_DUP
 static int
 ssl_dupAclChecklist(CRYPTO_EX_DATA *, const CRYPTO_EX_DATA *, void *,
                     int, long, void *)